import java.util.LinkedList;
import java.util.Queue;

class BinaryTree{

    static class TreeNode{

        public char val;

        public TreeNode left;

        public TreeNode right;

        public TreeNode(char val){
            this.val=val;
        }

    }


    public TreeNode createTree() {
        TreeNode treeNode1=new TreeNode('A');
        TreeNode treeNode2=new TreeNode('B');
        TreeNode treeNode3=new TreeNode('C');
        TreeNode treeNode4=new TreeNode('D');
        TreeNode treeNode5=new TreeNode('E');
        TreeNode treeNode6=new TreeNode('F');
        TreeNode treeNode7=new TreeNode('G');
        TreeNode treeNode8=new TreeNode('H');


        treeNode1.left=treeNode2;
        treeNode1.right=treeNode3;
        treeNode2.left=treeNode4;
        treeNode2.right=treeNode5;
        treeNode3.left=treeNode6;
        treeNode3.right=treeNode7;

        treeNode5.right=treeNode8;

        return treeNode1;
    }

    // 前序遍历
    public void preOrder(TreeNode root) {
        if(root==null)
            return;
        System.out.print(root.val+" ");
        preOrder(root.left);
        preOrder(root.right);
    }

    // 中序遍历
    void inOrder(TreeNode root) {
        if(root==null)
            return;
        inOrder(root.left);
        System.out.print(root.val+" ");
        inOrder(root.right);
    }

    // 后序遍历
    void postOrder(TreeNode root) {
        if (root==null)
            return;
        postOrder(root.left);
        postOrder(root.right);
        System.out.print(root.val+" ");
    }

    public static int nodeSize;

    /**
     * 获取树中节点的个数：遍历思路
     */
    void size(TreeNode root) {
        if(root==null)
            return;
        nodeSize++;
        size(root.left);
        size(root.right);
    }

    /**
     * 获取节点的个数：子问题的思路
     *
     * @param root
     * @return
     */
    int size2(TreeNode root) {
        if (root==null)
            return 0;
        return 1+size2(root.left)+size2(root.right);
    }


    /*
     获取叶子节点的个数：遍历思路
     */
    public static int leafSize = 0;

    void getLeafNodeCount1(TreeNode root) {
        if (root==null)
            return;
        if (root.left==null&&root.right==null)
            leafSize++;
        getLeafNodeCount1(root.left);
        getLeafNodeCount1(root.right);
    }

    /*
     获取叶子节点的个数：子问题
     */
    int getLeafNodeCount2(TreeNode root) {
        if (root==null)
            return 0;
        if (root.left==null&&root.right==null)
            return 1;
        return getLeafNodeCount2(root.left)+getLeafNodeCount2(root.right);
    }

    /*
    获取第K层节点的个数
     */
    int getKLevelNodeCount(TreeNode root, int k) {
        if (root==null)
            return 0;
        if (k==1)
            return 1;
        return getKLevelNodeCount(root.left,k-1)+getKLevelNodeCount(root.right,k-1);
    }

    /*
     获取二叉树的高度
     时间复杂度：O(N)
     */
    int getHeight(TreeNode root) {
        if (root==null)
            return 0;
        int heightl=getHeight(root.left);
        int heightr=getHeight(root.right);
        return heightr>heightl?heightr+1:heightl+1;
    }


    // 检测值为value的元素是否存在
    TreeNode find(TreeNode root, char val) {
        if (root==null)
            return null;
        if(root.val==val)
            return root;
        TreeNode findleft=find(root.left,val);
        if (findleft!=null)
            return findleft;
        return find(root.right,val);
    }

    //层序遍历
    void levelOrder(TreeNode root) {
        if (root==null)
            return;
        Queue<TreeNode> queue=new LinkedList<>();
        queue.add(root);
        while(!queue.isEmpty()){
            TreeNode treeNode=queue.poll();
            System.out.print(treeNode.val+" ");
            if (treeNode.left!=null){
                queue.add(treeNode.left);
            }
            if (treeNode.right!=null){
                queue.add(treeNode.right);
            }
        }

    }


    // 判断一棵树是不是完全二叉树
    boolean isCompleteTree(TreeNode root) {
        if(root==null)
            return true;
        int h=getHeight(root);
        int nodenum=size2(root);
        int node=1;
        while(h>=1){
            node*=2;
            --h;
        }
        node--;
        return node==nodenum;
    }



}






public class Main {
    public static void main(String[] args) {
        BinaryTree binaryTree=new BinaryTree();
        BinaryTree.TreeNode treeNode=binaryTree.createTree();

        binaryTree.preOrder(treeNode);
        System.out.println();

        binaryTree.inOrder(treeNode);
        System.out.println();

        binaryTree.postOrder(treeNode);
        System.out.println();

        binaryTree.size(treeNode);
        System.out.println(BinaryTree.nodeSize);

        System.out.println(binaryTree.size2(treeNode));

        binaryTree.getLeafNodeCount1(treeNode);
        System.out.println(BinaryTree.leafSize);

        System.out.println(binaryTree.getLeafNodeCount2(treeNode));

        System.out.println(binaryTree.getKLevelNodeCount(treeNode, 4));

        System.out.println(binaryTree.getHeight(treeNode));

        BinaryTree.TreeNode treeNode1=binaryTree.find(treeNode,'H');
        System.out.println(treeNode1!=null?treeNode1.val:null);

        binaryTree.levelOrder(treeNode);
        System.out.println();

        System.out.println(binaryTree.isCompleteTree(treeNode));

    }
}